CKEditor in ModalPopUpExtender

Hi,

Does anyone has a solution to the following issue. I have a Panel with ModalPopupExtender. Panel contains ckeditor control. The issue which i experience is when trying to select combo boxes (Font style, format, size, etc.) they appear behind the ModalPopupExtender (in Firefox 3.6, Opera 11, Chrome 9). IE 6 and IE 8 works well

Here's the piece of code:

<cc1:ModalPopupExtender ID="mdlPopup" PopupControlID="pnlEditText" TargetControlID="lnkBtnEditImageText" CancelControlID="lnkBtnCloseEditText" DropShadow="false" PopupDragHandleControlID="top" runat="server">
</cc1:ModalPopupExtender>                                                    
<asp:Panel ID="pnlEditText" runat="server" CssClass="modalpopup" 
Style="display: block;">
  <div id="top" runat="server">
     asp:LinkButton ID="lnkBtnCloseEditText" runat="server"></asp:LinkButton>
  </div>
   <CKEditor:CKEditorControl ID="editor" runat="server" Height="150px" Width="700px" AutoParagraph="False" ></CKEditor:CKEditorControl>   
</asp:Panel>